Method for exploring the surface of the earth with electromagnetic energy including comparing reradiation characteristics of gases to locate escaping hydrocarbon gases at the surface emitted by deposits of petroleum and/or natural gas at depth

ABSTRACT

The present invention makes use of the discovery of the fact that producing or potentially producing oil and/or gas fields usually have associated therewith at the earth&#39;&#39;s surface, the presence of escaping or permeating gases which have risen from underground stratigraphic and structural traps from which oil and/or natural gases may be recovered through drilled wells. Detection of the permeating gases is accomplished by focusing a beam of microwave radiation of known predetermined parameters thereupon, from remote locations, and measuring the parameters of the returned &#39;&#39;&#39;&#39;reflected&#39;&#39;&#39;&#39; microwave signals i.e., signals which are re-radiated by the hydrocarbons at the surface. Comparison of the frequency shift, and other parameters of the returned signal with the parameters of the transmitted microwave signal and correlation of the modified parameters of the returned wave with predetermined &#39;&#39;&#39;&#39;microwave re-radiation characteristics&#39;&#39;&#39;&#39; (MRC) of known gases will enable an immediate qualitative identification of a detected gas to be made and will enable an approximation of the quantitative concentrations of the detected gas to be made. Furthermore, by employing conventional navigational and cartographic procedures in association with the gas detecting practices of the present invention, it is possible to use ground vehicles and aircraft to explore, to prospect for, and to map gas and/or oil producing fields.

Owen et al.

States atent 51 Mar. 21, 1972 [54] METHOD FOR EXPLORING THE SURFACE OFTHE EARTH WITH ELECTROMAGNETIC ENERGY INCLUDING COMPARING RERADIATIONCHARACTERISTICS OF GASES T0 LOCATE ESCAPING HYDROCARBON GASES AT THESURFACE EMITTED BY DEPOSITS OF PETROLEUM AND/OR NATURAL GAS 3,392,3847/1968 Wesch 324/6 X Primary Examiner-Gerard R. StreckerAttorneyMandeville and Schweitzer [5 7] ABSTRACT The present inventionmakes use of the discovery of the fact that producing or potentiallyproducing oil and/or gas fields usually have associated therewith at theearth's surface, the presence of escaping or permeating gases which haverisen from underground stratigraphic and structural traps from AT DEPTHwhich oil and/or natural gases may be recovered through [72] Inventors;Robert L, Owen, New York, N,Y J lia drilled wells. Detection of thepermeating gases is accom M. Busby, Mu kogee, Okla, V plished byfocusing a beam of microwave radiation of known predetermined parametersthereupon, from remote locations, [73] Asslgnee' Advanced New York andmeasuring the parameters of the returned "reflected" by Sald WFLW,microwave signals i.e., signals which are re-radiated by the [22] Filed;Sept 12, 9 hydrocarbons at the surface. Comparison of the frequencyshift, and other parameters of the returned signal with the PP NO I857,488 parameters of the transmitted microwave signal and correlationof the modified parameters of the returned wave with [52] predeterminedmicrowave re-radiation characteristics" [51] (MRC) of known gases willenable an immediate qualitative 58] identification of a detected gas tobe made and will enable an approximation of the quantitativeconcentrations of the de- [56] References Cited tected gas to be made.Furthermore, by employing conventional navigational and cartographicprocedures in association UNITED STATES PATENTS with the gas detectingpractices of the present invention, it is possible to use round vehiclesand aircraft to ex lore, to

g P gf p i prospect for, and to map gas and/or oil producing fields. auet a 3,351,936 11/1967 Feder ..324/6 X 6 Claims, 2 Drawing FiguresM/CROWA l/E f CAOh/A VF .s/G/VAL TAA/l/SM/TTE)? PECf/VE/P Ali AL YZfz? JRECORDER 4 ALf/fl/DE [DAG/700E 5 k r G6 men/Is sue/=40? H METHOD EOEEXPLORING THE SURFACE OF THE EARTH WllTlIil ELECTROMAGNETIC ENERGYINCLUDING COMPARHNG RERADIATION CHARACTERTSTHCS OF GASES TO LOCATEESCAPllNG HYDROCAEBON GASES AT THE SURFACE EMITTED BY DEPOSITS OEPETROLEUM AND/OR NATURAL GAS AT DEPTH BACKGROUND OF THE INVENTIONHeretofore, the oil and gas prospecting industry in its explorations hasconstantly sought structural underground traps, utilizing seismographicmethods, since this has been the easi est and most feasible way todiscover the presence of oil and/or gas deposits. In the past, theindustry made very little effort to discover stratigraphic traps. Theexplanation for this is, of course, quite logical, since the task oflocating a stratigraphic trap is quite formidable and until now, noworkable, economically feasible, geological, geochemical or geophysicalmethod of discovering a stratigraphic trap had been successfullyutilized by the art. More importantly, structural traps heretofore haveprovided the industry with a relatively high success ratio. That is tosay, a successfully drilled structural trap often contains more than oneproducing horizon. In other words, the penetration of a structural trapat a single location often turns up a plurality of reservoirs stackedone upon the other, whereas stratigraphic traps are rarely stacked inthis fashion.

Since long established, well accepted geophysical methods have beencomparatively successful in the discovery of structural traps and sincesuch structural traps have been comparatively more fruitful in terms ofproduction than stratigraphic traps, the efforts of the industry and thegeophysicists working therein have been almost exclusively confined tothe development and improvement of methods and apparatus for discoveringthe location of underground structural traps which methods and apparatushave been unsuccessful for discovering stratigraphic traps.

As a matter of fact, throughout the world, the major new oil discoveriescontinue to be predominantly in the form of structural traps of theanticlinal type. For example, the latest discoveries in offshoreAustralia, West Africa, Egypt, Russia, and Libya are all structuraltraps which were discovered by virtue of their structural features. Suchstructural features are conventionally and comparatively readilydiscoverable by the use of well-known well established seismictechniques. Thus, for example, the latest oil fields discovered in SouthAmerica have been uncovered by the use of seismic technology as have thelatest discovered gas and oil fields in the English channel offshorefrom Holland and from England. Likewise, offshore searches are currentlybeing made in Brazilian and Venezuelian waters, as well as in theoffshore gulf coastal waters and offshore California waters of theUnited States utilizing seismic exploration. The seismographical methodsemployed to discover the known structural traps have been used for many,many years starting in early 1920 to 1925 when the refractionseismograph was first introduced in America by German geophysicists.This geophysical aid has had a remarkable record of success in thediscovery of new gas and oil fields, especially in hard access areassuch as offshore areas and inland areas under cover where geologists hadlittle or no outcrops or dryholes with which to ascertain structuralfeatures. However, seismographic exploration cannot be employed wherethe surface rocks are not receptive to this type of exploration.

In addition to the aforementioned seismic exploration or prospectingmethods, magnetic and gravity methods have been long used for geologicalreconnaissance. As is well known in the geophysical arts, the magnetictechniques employ the measurement of the magnetic attraction of buriedmasses of igneous rocks or iron bearing near surface rocks that exceed aso-called normal level. Deviations in the pull of gravity of massiveunderground igneous bodies or lighter salt intrusions create anomaliesfrom what would normally be expected in terms of gravity attraction ofnon-anomalous geological structures is an indication of the possiblepresence of an anticlinal or faulted feature.

In the past, geophysicists using the above outlined methods, have beenable to select what appear to be favorable places to prospect for oiland gas. Likely looking areas were thoroughly surveyed by seismicmethods to determine details of the struc tural traps, i.e., to definethe depths and attitudes of the strata, the shapes of the submergedmasses, etc. Of course. with these methods, the ultimate determinationof the presence or absence of gas or oil is only made by actuallydrilling in the prospective area to determine the presence of gas oroil. The aforementioned geophysical methods of locating and defining thestructural features of structural traps have been of little use inlocating and defining stratigraphic traps and have been of limited or nouse for subsurface structural determination when surface rocks arenon-compatible to seismic investigation. Since it is accepted by manyAmerican geologists that almost all of the structural traps in thecontinental United States have been found, and that the location of asyet undiscovered structural traps is extremely difiicult by knownconventional methods, it is apparent that the search for oil and gasfields in the continental United States should now logically beconcentrated on the search for other types of traps than structuraltraps, namely stratigraphic traps or that new methods and apparatus fordiscovering structural traps be developed. Furthermore, it is notunlikely that many stratigraphic and structural traps that have yet tobe discovered actually exist in or around known American oil fields.Accordingly, it is to a new and improved method and apparatus forlocating and defining stratigraphic and structural traps that thepresent invention is directed.

SUMMARY OF THE INVENTION It has been discovered that underground trapsvery usually leak petroleum and/or natural gases up through theoverlying rocks to the surface of the earth. These escaping gases havewell definable and ascertainable microwave re-radiation characteristics(MRC) which may be used to enormous advantage in the prospecting for oiland gas by remote sensing. That is to say, that at a predeterminedmicrowave wavelength, a gas will have unique and measurable radiationqualities. These qualities are employable in the practice of theinvention to enable geophysicists to determine the presence of anescaping gas, the identity of the escaping gas, and the approximateconcentration of the gas above the deposit from which the escaping gasemanates. While the practice of the invention may be carried out withradiated microwave energy, which as will be readily understood, may bebeamed at or along the earth's surface from highly remote locations suchas from mountain tops, moving or stationary ground vehicles, aircraft,and the like, it should be understood that higher frequency, shorterwavelength energy in the light portions of the spectrum may be employedfor the same purposes once the wave reflection characteristics" for theparticular type and level of energy of the transmitted beam have beenascertained by geophysicists.

Remote and geophysical prospecting for unknown stratigraphic andstructural traps is carried out in accordance with the principles of theinvention, as follows. A transmitted beam of microwave energy (orshorter wavelength, higher frequency energy if desired) is beamed from adistance and focused upon the area under investigation. By the use ofproper circuitry, re-radiation by the atomic structure of hydrocarbongases caused by the incident beam of radiation from the transmitter (notfrom hard targets) may be appropriately detected by a microwave receivertuned to the frequency or frequency band of the MRC response sought.That is to say, if a single species of gas is being sought, theapparatus being used to discover the presence of that gas will be highlytuned to detect only its presence through its peculiar microwavereradiation characteristics" and not the presence of other gases orother hard targets. Alternatively, if the prospecting in or theexploring of an area is being done to find the presence of any ofseveral different species of escaping gases, the apparatus employed willinclude a transmitter capable of transmitting beams of microwave energyof known, predetermined parameters on a plurality of wavelengthsthroughout the microwave spectrum or throughout a predetermined limitedband within the microwave spectrum and it will include a receivingapparatus which is adapted to receive the re-radiation of gases in theirrespective bandwidths. As will be understood, the re-radiated beamreceived will possess different parameters (frequency, power, etc.) fromthose of the transmitted beam, the difference in the frequencies being afunction of the MRC of the detected gas and being a useful determinantof the specific identity of the detected gas. In addition toqualitatively identifying the species of the gas escaping at the surfacefrom an underground stratigraphic trap, the method of the invention,utilizing the specific parameters, i.e., frequency shift, power, waveshape, etc. of the returned reflected microwave signal, will provide aquantitative indication of the concentrations of the escaping gas at thesurface from the stratigraphic or structural trap, itself.

By utilizing the method of the present invention in conjunction withwell-known cartographic surveying procedures, it will be readilypossible to easily map surveyed areas geographically, for the presenceof areas in which escaping gases indicative of underground traps exist.Using this information, it will, of course, be a simple matter todevelop maps and drill wells in those areas where escaping gases havebeen located to exploit the presence of a field. Unlike the previousseismic and other conventional methods employed to discover structuraltraps, which methods, in effect, mapped detected possible subsurfacegeological structural features, which features geophysicists byinduction determined were likely to contain oil, the present methoddetermines absolutely the underground presence of a source ofhydrocarbon gases originating from a deposit ofgas and/or oil,

DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic block diagram ofapparatus of the invention used for the practice of the new method forprospecting for underground stratigraphic and structural traps; and

FIG. 2 is a schematic block diagram of an alternate embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION Apparatus of the preferredembodiment of the invention includes a microwave transmitter which maybe of readily, commercially available construction and a microwavereceiver 12 which also may be of readily, commercially availableconstruction. Thus, the transmitter can be chosen and operated totransmit continuously or to transmit in bursts or pulses of microwaveenergy. In the embodiment illustrated in FIG. 1, the transmitter 10 andreceiver 12 share a common parabolic antenna 11, which transmits ahighly concentrated beam of microwave energy, having known predeterminedparameters, generated by the transmitter 10.

The high frequency, microwavelength energy is directed towards theearths surface at a predetermined microwave frequency F The beamedmicrowave energy strikes escaping gases G, if present, at the earthssurface. When a gas is present, the incident microwave energy will bemodified in accordance with its microwave re-radiation characteristics"and reflected," i.e., re-radiated, back to the antenna 11. Thereflected" waves will possess modified parameters, (including a shiftedfrequency F in comparison to those of the incident waves. As will beunderstood and in accordance with the invention, the precise differencesin the parameters will be a function of the quality and quantity,specific gas, its microwave re-radiation characteristics (MRC) which maybe empirically determined and tabulated in advance.

The received signal is conducted from the antenna 11 to a receiver 12where its precise parameters are detected. As a most important aspect ofthe invention, these detected parameters including the degree offrequency shift from the transmitted frequency F to the reflectedfrequency F 2 are employed in the analysis of the detected gas G. Thedegree of frequency shift as well as the degree of attenuation of thetransmitted wave as reflected from the gas G, functions of the MRC, willbe indicative, in accordance with the principles of the invention, ofboth the identity of the escaping gas G and of an approximation of thequantity of the presence thereof. As will be appreciated, the returned,reflected signal may be amplified through suitable apparatus and itsparameters ascertained through signal analyzing and measuring equipmentsuch as a power meter 13 and recorded on a suitable multichannelrecorder 14. Alternatively or additionally, the reflected" signal may bedisplayed on an oscilloscope or other graphic display device.

In accordance with the principles of the invention, the prospectingapparatus disclosed in FIG. 1 may be mounted in an aircraft forexploring vast areas in short order. Altematively, the apparatus may bemounted in a fixed station at a vantage point which overlooks largeareas such as a mountain peak or in an elevated location such as atower. Of course, when deemed necessary or desirable, the apparatus ofthe invention may be mounted in a truck or other motor vehicle forsurveying prospective oil and/or gas producing fields by actuallydriving over the terrain thereof.

When the apparatus is employed in conjunction with an aircraft foraerial surveying and prospecting, suitable recording of the altitude,latitude and longitude of the aircraft may be made contemporaneouslywith the recording of the data generated by the transmitter andreceiver. Apparatus for detecting and recording the altitude, latitudeand longitude coordinates of the surveying vehicle (aircraft or motorvehicle) is indicated schematically in FIG. 1 at 15 and I6. In thismanner, detected gases may be located by geographic coordinates andelevations which will, of course, enable hypsometric maps of discoveredfields to be drawn with facility and accuracy.

In FIG. 2, an alternate embodiment of the invention is depicted. Thesystem of FIG. 2 includes a pair ofantennas 21, 22 mounted side-by-sidein a bi-static arrangement to form a line at right angles to theprinciple flight path axis or vehicle path axis of the aircraft orvehicle in which the apparatus is mounted. Each of the antennas 21, 22is a readily available parabolic antenna of the type used in connectionwith microwave transmission and reception. A microwave transmitter 20 isassociated with the antenna 21 for the generation and radiation of abeam of microwaves downwardly towards the area being surveyed.

As will be understood, the antenna 22 is focused to receive re-radiatedbeams of radiation from escaping gases. Such reflected signals areconducted from the antenna 22 to a microwave receiver 23 where thesignal is amplified before it is transmitted to the power meter 24 orother parameter analyzing and measuring equipment, where the variousparameters of detected, reflected microwave F are measured. The measuredparameters may be recorded on a moving tape or other suitable medium ina conventional multichannel recording apparatus indicated schematicallyat 25.

In accordance with the principles of the invention, the apparatus isarranged and operated to detect only beams of microwave energyre-radiated from escaping gases; all hard targets are not detected bythe apparatus. Accordingly, when no gases are present beneath theantenna 21 and in the paths of the beamed energy at frequency F,emanating therefrom, no reflection will be detected by the receiver 23,which will be sharply tuned for the detection only of microwave energyfrom escaping gases having a predetermined MRC or range of MRC. Thereflected, i.e., re-radiated, return signals may be displayedimmediately upon an oscilloscope, such as a plan position indicator, forobtaining an immediate readout" of the signals detected by the apparatusof the invention contemporaneously with the recording thereof byrecorder 25. Moreover, permanent records of the traces of theoscilloscope may be obtained by photographic techniques, which alsocould be used simultaneously to record the readings of altitude,latitude and longitude indicators 26, 27. Where this type ofphotographic recording of data is employed, a suitable prismaticarrangement may be developed in order to simultaneously aeriallyphotograph the terrain at which the presence of a gas has been detected.

By way of a concrete example, the method of the present invention hasbeen practiced by irradiating terrain under exploration from a surveyingstation located approximately 2,000 feet away. The surveying station"was at ground level relative to the terrain under exploration. Theequipment at the surveying station included atransmitter, transmittingantenna, receiver, receiver antenna, and associated apparatus such asplan-position indicator and power sources.

The transmitter broadcast a signal E, having the following parameters:9,375 megacycle frequency; being a wavelength of 1.2570624 inches or3.1929448 centimeters; power of kw. The receiver detected reflected,i.e., re-radiated, signals F from escaped natural gas, which signal hadthe following parameters: Afrequency of 9361 megacycles or a wavelengthof 1.2589424 inches or 3. 1977291 centimeters.

The differences between F, and F were due to the MRC of the detectedgases at the broadcast parameters. No signals from hard targets" weredetected by the receiver because the receiving apparatus was tuned to9,361 mc. and could not receive any re-radiated electromagnetic waves onthe broadcast frequency of 9,375.

A test bore drilled at a site in which escaping gases indicated thepresence of underground deposits of gas and/or oil verified theexistence of such deposits at a depth of 870 feet.

It will be appreciated that suitable circuitry or available equipmentcan be employed to completely automate the exploration process of theinvention, That is to say, the detection and recording apparatus may beprecalibrated to select and record (and/or display) only returnedreflected signals indicating an oil or gas deposit having predeterminedminimum properties in terms of potential production. In other words, theapparatus will have built-in" to it by the inclusion of appropriatecircuitry or components, facilities for comparing or ascertaining thedifferences between the incident and reflected microwave energy andcorrelating the same, based on known MRC values, to determine thelocation of large oil and/or gas fields. Thus apparatus having grossgo-no go (oilno oil) detection capabilities, can be produced for use byrelatively unskilled personnel.

While the foregoing disclosure has been directed to new methods andapparatus for gas and oil exploration; it should be understood thatsimilar techniques and equipment may be used in prospecting for otherunderground mineral deposits. That is to say, many mineral deposits areconstantly subject to chemical reactions, namely oxidation, which tendto liberate gases which escape to the earths surface by permeatingthrough the overlying soil and rocks. Utilizing the MRC of the gasesescaping from underground mineral deposits, an evaluation of the qualityand quantity of the deposit may be made.

A further use for the method and apparatus of the present invention isin the prevention of drilling dry holes" in areas previously prospectedby conventional methods. Thus where a seismic exploration, for example,would suggest the presence of an oil or gas field, it is a simple matterto verify the presence or absence of gas or oil by the practice of thepresent invention, rather than by the costly and time consuming. actualdrilling of a test bore. Thus, the apparatus of the invention may beimmediately employed in the go-no go (oil-no oil) sense to supplementconventional exploration techniques.

A still further more limited application of the techniques of theinvention is for the aerial surveillance of gas pipe lines. While thepresence of leaks somewhere within the line can be detected by ameasured pressure drop, the actual locating of the point or points ofleakage is a difficult undertaking. As will be readily appreciated,rather than inspecting a pipe line slowly and visually, a quick andefficient inspection of an entire pipe line may be made from an aircraftequipped with appropriate microwave transmitting and receiving apparatussuitably tuned in accordance with MRC of the piped gas.

It is to be understood, of course, that the method and apparatus hereinillustrated and described are intended to be representative only, ascertain changes may be made therein without departing from the clearteachings of the disclosure. Accordingly, reference should be made tothe'follbwing ap pended claims in determining the full scope of theinvention.

We claim:

1. A method of locating underground gas, oil, or mineral depositscomprising the steps of a. generating a beam of incident microwaveenergy having predetermined parameters including a first frequency;

b. focusing and radiating said beam of incident microwave energy havingpredetermined parameters upon the escaping gases at the surface ofterrain under exploration and thereby causing said gases to re-radiatesaid energy at second and different frequencies; detecting microwaveenergy from re-radiated at said different frequencies gases at thesurface of the terrain under exploration;

d. measuring certain parameters of said detected microwave energyincluding at least the re-radiated frequencies thereof; and

. correlating the parameters of said incident and re-radiation microwaveenergy including the frequency differentials between the incident andre-radiated energies, with predetermined microwave re-radiationcharacteristics of selected gases.

. The method of claim 1, in which a. said radiated microwave energy isgenerated remotely of and at elevated altitudes with respect to theterrain under exploration;

b. said reflected microwave energy is detected remotely of and atelevated altitudes with respect to the escaping gases at the surface ofthe terrain under exploration.

3. The method of claim 1, in which a. said microwave energy iscontinuously transmitted.

4. The method of claim 1, in which a. said microwave energy isintermittently transmitted.

5. The method of claim 1, in which a. a single species of gas is sought;

b. said microwave energy is transmitted and detected over narrowbandwidths determined at least in part by the microwave re-radiationcharacteristics of said single species of gas.

6. The method of claim 1, in which a. any one of several species ofgases is sought;

b. said microwave energy is transmitted and detected over bandwidthsdetermined at least in part by the spectrum of microwave re-radiationcharacteristics of the several species of gases.

PO-105O (5/89, UNHTED STA'EEd PATENT sw CERTEFEQATE @IF CRRCTEN PatentNo. 3r65lv395 Dgatgfi March 21, 1972 Robert L. Owen and Julian Mn BusbyInventofls) It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shoim below:

Column 6, lines 31 and 32 c detecting microwave energy from re-radiatedat said different frequencies gases at the surface of the terrain"should read c. detecting microwave energy re-radiated at said differentfrequencies from gases at the surface of the terrain.,

Signed and sealed this 23rd day of January 1973.

(SEAL) Attest:

EDWARD M.PLETCHER,JR., ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents (5/69) TED STATES PATENT @FFEEE t'rrrrtrrr r toners PatentNo, 51,395 pm; & March 21, 1972 Robert L. Owen and Julian Ma BusbyInventofls) It is certified that error appeara in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Column 6, lines 31 and 32 0., detecting microwave energy fromre-radiated at said different frequencies gases at the surface of theterrain" should read --co detecting microwave energy re-radiated at saiddifferent frequencies from gases at the surface of the terrain-n Signedand sealed this 23rd day of January 1973.

(SEAL) Attes't:

EDWARD M .FLETCHER,JR.. Attesting Officer ROBERT GOTTSCHALK Commissionerof Patents

2. The method of claim 1, in which a. said radiated microwave energy isgenerated remotely of and at elevated altitudes with respect to theterrain under exploration; b. said reflected microwave energy isdetected remotely of and at elevated altitudes with respect to theescaping gases at the surface of the terrain under exploration.
 3. Themethod of claim 1, in which a. said microwave energy is continuouslytransmitted.
 4. The method of claim 1, in which a. said microwave energyis intermittently transmitted.
 5. The method of claim 1, in which a. asingle species of gas is sought; b. said microwave energy is transmittedand detected over narrow bandwidths determined at least in part by themicrowave re-radiation characteristics of said single species of gas. 6.The method of claim 1, in which a. any one of several species of gasesis sought; b. said microwave energy is transmitted and detected overbandwidths determined at least in part by the spectrum of microwavere-radiation characteristics of the several species of gases.